package client.net.sf.saxon.ce.expr.sort;
import client.net.sf.saxon.ce.lib.StringCollator;
import client.net.sf.saxon.ce.value.AtomicValue;
import client.net.sf.saxon.ce.value.StringValue;
import client.net.sf.saxon.ce.expr.XPathContext;
import client.net.sf.saxon.ce.trans.NoDynamicContextException;
/**
* A Comparer used for comparing sort keys when data-type="text". The items to be
* compared are converted to strings, and the strings are then compared using an
* underlying collator
*
* @author Michael H. Kay
*
*/
public class TextComparer implements AtomicComparer {
private AtomicComparer baseComparer;
public TextComparer(AtomicComparer baseComparer) {
this.baseComparer = baseComparer;
}
/**
* Get the underlying comparer (which doesn't do conversion to string)
*/
public AtomicComparer getBaseComparer() {
return baseComparer;
}
public StringCollator getCollator() {
return baseComparer.getCollator();
}
/**
* Supply the dynamic context in case this is needed for the comparison
* @param context the dynamic evaluation context
* @return either the original AtomicComparer, or a new AtomicComparer in which the context
* is known. The original AtomicComparer is not modified
* @throws client.net.sf.saxon.ce.trans.NoDynamicContextException if the context is an "early evaluation" (compile-time) context
*/
public AtomicComparer provideContext(XPathContext context) {
AtomicComparer newBase = baseComparer.provideContext(context);
if (newBase != baseComparer) {
return new TextComparer(newBase);
} else {
return this;
}
}
/**
* Compare two Items by converting them to strings and comparing the string values.
* @param a the first Item to be compared.
* @param b the second Item to be compared.
* @return <0 if a<b, 0 if a=b, >0 if a>b
* @throws ClassCastException if the objects are not Items, or are items that cannot be convered
* to strings (e.g. QNames)
*/
public int compareAtomicValues(AtomicValue a, AtomicValue b) throws ClassCastException, NoDynamicContextException {
return baseComparer.compareAtomicValues(toStringValue(a), toStringValue(b));
}
private StringValue toStringValue(AtomicValue a) {
if (a instanceof StringValue) {
return ((StringValue)a);
} else {
return new StringValue((a == null ? "" : a.getStringValue()));
}
}
/**
* Compare two AtomicValue objects for equality according to the rules for their data type. UntypedAtomic
* values are compared by converting to the type of the other operand.
*
* @param a the first object to be compared.
* @param b the second object to be compared.
* @return true if the values are equal, false if not
* @throws ClassCastException if the objects are not comparable
*/
public boolean comparesEqual(AtomicValue a, AtomicValue b) throws NoDynamicContextException {
return compareAtomicValues(a, b) == 0;
}
/**
* Get a comparison key for an object. This must satisfy the rule that if two objects are equal
* according to the XPath eq operator, then their comparison keys are equal according to the Java
* equals() method, and vice versa. There is no requirement that the
* comparison keys should reflect the ordering of the underlying objects.
*/
public ComparisonKey getComparisonKey(AtomicValue a) throws NoDynamicContextException{
return baseComparer.getComparisonKey(toStringValue(a));
}
}
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is “Incompatible With Secondary Licenses”, as defined by the Mozilla Public License, v. 2.0.